Xijing Hospital Air Force Medical University Xi’an, Shaanxi
W. Wang, and Z. Wang; Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, Xian, Shaanxi, China
Purpose/Objective(s): An new integrated accelerator and a non-invasive stereotactic radiosurgery instrument radiotherapy platform has been put into clinical use. The aim of this study is to explore the dosimetric advantages of this technology in the simultaneous integrated boost planning of brain metastases. Materials/
Methods: Ten patients with brain metastases were randomly selected for whole brain irradiation with integrated boost. The prescription of PTV-brain and PGTV was 30Gy/10F and 40Gy/10F. The VMAT technology was used in the conventional treatment plan. X-ray and ?-ray multi-mode radiotherapy technology was used in the combined treatment plan. The target PGTV was irradiated with a non-invasive stereotactic radiosurgery instrument, and on this basis, the accelerator plan was optimized by VMAT technology to cover the target PTV-brain. The target dose distribution and dose of organs at risk (OARS) of two plans were compared, and the ability that to reduce the dose to organs at risk while increasing the dose to the target was evaluated. Results: All treatment plan met clinical requirements. Compared with conventional VMAT plan, the combined treatment plan that made by radiotherapy platform had similar conformance (CI):(0.836±0.104 vs 0.826±0.038, p=0.737); and significantly lower gradient index (GI) :( 3.988±0.969 vs 5.245±1.875, p=0.008). The combined treatment plan had similar Dmean of PTV-brain (30.33±2.14 vs 30.23±1.67, p = 0.016) and significantly higher Dmean of PGTV (45.18±0.71 vs 41.17±0.31 , p = 0.001). In terms of organs at risk, of brainstem Dmax(38.98±10.23 vs 42.34±9.75, p = 0.052) ; chiasmas Dmax (32.14±5.87 vs 32.92±6.68, p = 0.067); Left optic nerve Dmax(23.51±2.21 vs 23.48±2.18, p = 0.024) ; Right optic nerve Dmax (23.40±2.17 vs 23.35±2.26); The the left lens Dmax (4.23±2.18 vs 5.79±2.09, p = 0.024); the righ lens Dmax (4.23±2.22 vs 5.54±2.19 ,p = 0.016). Conclusion: This new multimodal radiotherapy technology is feasible to increase the dose to the target volume and reduce the dose to the organs at risk.
